Plant Services - May 2008 - (Page 32) xperts are quick to point out that the biggest gains to be made in compressed-air system energy efficiency are on the demand side. Most plants are running too much pressure, are full of leaks and are using compressed air for purposes where less energyintensive options exist. And Plant Services has published thousands of words about where to find and how to fi x those demand-side excesses. But the fact that the demand side is by far the larger part of the problem hasn’t fazed the engineers who toil daily to increase the efficiency of the compressors themselves. And like good engineers always do, they’ve made quiet but excellent progress during the past 20 years. E Drive down kW per 100 cfm By Paul Studebaker, CMRP, Editor in Chief From inlet fi lters to oil separators, airends to controls, compressor and compressed-air equipment manufacturers are driving down the amount of energy it takes to generate a given flow – your kW per 100 cfm. Here’s how they say they’re doing it, and what you need to know to take advantage of their labors. Principles start with p A few percent here, a few percent there – it doesn’t sound like much, but over time, efficiency makes a big difference because the purchase price of a compressor pales in the face of its life cycle cost. “What’s the cost of a compressor?” says Mike Bakalyar, manager, enhanced services, Gardner Denver (www.gardnerden ver.com). “Over its life, a 150 hp machine at $0.10/kWh will cost $1.2 million.” Some of those percentage improvements are obtained by limiting pressures. Minimizing the maximum compression pressure has a direct and well-known relationship with efficiency – the guideline is that every 2 psi reduction increases efficiency 1%. Annual savings from reducing a pressure drop between the airend and the point of use is shown in Table 1. “It’s all about specific performance,” says Harold Wagner, national sales manager, Kaeser (www.kaeser.com). “You must compare the total amount of energy put into a compressor to produce the compressed air at the specified pressure at the compressor discharge. at includes everything from cooling fans to drive motors and transmission losses.” 32 .PLANTSERVICES. M http://www.gardnerdenver.com http://www.gardnerdenver.com http://www.kaeser.com http://www.plantservices.com
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